Background Progression of atherosclerosis is associated with a greater risk for adverse outcomes. Angiotensin II plays a key role in the pathogenesis and progression of atherosclerosis. We aimed to investigate the effects of angiotensin II type-1 receptor blockade with Valsartan on carotid wall atherosclerosis, with the hypothesis that Valsartan will reduce progression of atherosclerosis. Methods Subjects (n = 120) with carotid intima-media thickness >0.65 mm by ultrasound were randomized (2:1) in a double-blind manner to receive either Valsartan or placebo for 2 years. Bilateral T2-weighted black-blood carotid magnetic resonance imaging was performed at baseline, 12 and 24 months. Changes in the carotid bulb vessel wall area and wall thickness were primary endpoints. Secondary endpoints included changes in carotid plaque thickness, plasma levels of aminothiols, C-reactive protein, fibrinogen, and endothelium-dependent and -independent vascular function. Results Over 2 years, the carotid bulb vessel wall area decreased with Valsartan (-6.7, 95% CI [-11.6, -1.9] mm2) but not with placebo (3.4, 95% CI [-2.8, 9.6] mm2), P =.01 between groups. Similarly, mean wall thickness decreased with Valsartan (-0.18, 95% CI [-0.30, -0.06] mm), but not with placebo (0.08, 95% CI [-0.07, 0.23] mm), P =.009 between groups. Furthermore, plaque thickness decreased with Valsartan (-0.35, 95% CI [-0.63, -0.08] mm) but was unchanged with placebo (+0.28, 95% CI [-0.11, 0.69] mm), P =.01 between groups. These findings were unaffected by statin therapy or changes in blood pressure. Notably, there were significant improvements in the aminothiol cysteineglutathione disulfide, and trends to improvements in fibrinogen levels and endothelium-independent vascular function. Conclusions In subjects with carotid wall thickening, angiotensin II type-1 receptor blockade was associated with regression in carotid atherosclerosis. Whether these effects translate into improved outcomes in subjects with subclinical atherosclerosis warrants investigation.